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<p>This study investigated the connections between interannual variations in June precipitation in Northern China (NC) and soil moisture (SM) over Eurasia. Using empirical orthogonal function (EOF) analysis, we identified three dominant modes of June precipitation in NC: a spatially coherent pattern, a north–south dipole, and an east–west dipole. These modes were significantly correlated with SM anomalies from April to June in three key regions: the middle and lower reaches of the Yangtze River (MLYR), the Iranian Plateau, and Central Asia. Anomalously wet (dry) SM levels altered the surface energy balance by modulating the sensible and latent heat fluxes, and enhanced (suppressed) convection and precipitation. These thermal anomalies induced by anomalously wet (dry) SM persisted from May to June, leading to decreases (increases) in atmospheric thickness and modulating baroclinicity around the three key regions. Consequently, the thermal anomalies modulated wave train propagation along the mid-latitude westerly jet from Europe to NC. The distinct positions and intensities of these wave trains for each key region corresponded to the top three EOF modes of June precipitation in NC. Analysis of local energy conversion showed that SM-induced diabatic heating affected wave train maintenance by modulating the generation and conversion of eddy available potential energy. Results also showed that favorable conditions for each of the three observed EOF precipitation modes were established through the modulation of upper-level divergence fields around NC by the wave trains, in combination with low-level water vapor transport.</p>

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Impact of soil moisture anomalies over Eurasia on June precipitation in Northern China and its mechanism

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Kechen Li,
  • Kai Yang,
  • Yanhui Zhang

摘要

This study investigated the connections between interannual variations in June precipitation in Northern China (NC) and soil moisture (SM) over Eurasia. Using empirical orthogonal function (EOF) analysis, we identified three dominant modes of June precipitation in NC: a spatially coherent pattern, a north–south dipole, and an east–west dipole. These modes were significantly correlated with SM anomalies from April to June in three key regions: the middle and lower reaches of the Yangtze River (MLYR), the Iranian Plateau, and Central Asia. Anomalously wet (dry) SM levels altered the surface energy balance by modulating the sensible and latent heat fluxes, and enhanced (suppressed) convection and precipitation. These thermal anomalies induced by anomalously wet (dry) SM persisted from May to June, leading to decreases (increases) in atmospheric thickness and modulating baroclinicity around the three key regions. Consequently, the thermal anomalies modulated wave train propagation along the mid-latitude westerly jet from Europe to NC. The distinct positions and intensities of these wave trains for each key region corresponded to the top three EOF modes of June precipitation in NC. Analysis of local energy conversion showed that SM-induced diabatic heating affected wave train maintenance by modulating the generation and conversion of eddy available potential energy. Results also showed that favorable conditions for each of the three observed EOF precipitation modes were established through the modulation of upper-level divergence fields around NC by the wave trains, in combination with low-level water vapor transport.